An ultra-fast interrogation method for a weak fiber Bragg grating array using an on-chip integrated DFB laser array

We propose an ultra-fast interrogation method for a weak fiber Bragg grating (WFBG) array based on a self-designed distributed feedback multi-wavelength laser array (DFB-MLA) chip. The laser integrates eight wavelength channels with a uniform wavelength interval of 0.13 nm, which is precisely controlled using the reconstruction-equivalent-chirp (REC) technique. Each channel is cascaded with a semiconductor optical amplifier (SOA) functioning as an optical shutter (referred to as s-SOA). The outputs of all 8 channels are combined into one waveguide via three Y-junction combiners and are then cascaded with another SOA functioning as an intensity modulator (referred to as m-SOA). The DFB-MLA emits eight wavelengths simultaneously. The s-SOAs cyclically enable the output of these wavelengths, and the m-SOA modulates each output beam into optical pulses. By sequentially injecting these pulses into a WFBG array and detecting the reflected signals, the position and wavelength shift of each WFBG can be accurately determined. In experiments, we achieve 1 MHz demodulation rate for 10 WFBGs, with a wavelength stability of ±5 pm, which represents one of the highest demodulation capacities reported for WFBG interrogation systems with a compact and low-complexity architecture. This technology enables high-precision, real-time tracking of ultra-high-frequency vibrations using a compact system configuration, opening wide application opportunities in structural health monitoring.